The present invention has been developed for use with the slant wells currently being drilled to exploit shallow heavy oil deposits, such as those in the vicinity of Bonnyville, Alberta.
The adoption of slant wells has come about in connection with thermal projects. Where steam is being injected into the producing formation, it is desirable to locate the wells as close to the steam generating facility as possible. This has led to the conception of grouping the well heads at the site of the steam generator and drilling directionally from that point to the subsurface target. As the wells are usually quite shallow and the needed angularity of the well bore is quite large, conventional whip-stocking of a well initiated at surface in a vertical direction has not been found suitable. This has led to the drilling of wells slanted right from surface using specially built slant rigs.
The present pumping unit has been developed to reciprocate the rod string used in such a slant well bore.
In designing the pumping unit, several requirements should be taken into account.
Firstly, the wells at a site will normally be drilled at different angles. These well bore angles might vary anywhere from 0.degree. to 40.degree. from vertical. Therefore it is desirable that the pumping unit be adjustable, to accommodate these variations.
Secondly, the pumping unit has to provide ample clearance around the well head in both the vertical and horizontal directions. The well head equipment on a thermal well is usually quite bulky and thus the horsehead has to be located at a relatively high position. Also, since the well head could be rearwardly slanted, the pumping unit base and crank have to be far enough removed so as not to interfere with the well head.
Thirdly, as is true of any pumping unit, it should be light in weight, efficient, and characterized by good torque and rod loading performance.